Hi,

I have a question about data for my thesis and I'm new with Stata!

I have to observe whether or not there occured a rotation of the auditor. To do that, I have data of companies for 2017 and 2018 (which audit firm they have in those years), to decide whether or not there has been a change. With some of the companies there is no data of 2018, which means that those companies need to be excluded. Does anyone maybe know how to exclude such observations? (in this pic, you can see that there is no data for company 0000033073 for 2018, for example).
Array

PS: after that, I want to create a dummy which is equal to 1 if the audit firm in 2018 is different from 2017, also for that I don't know what to use.

I hope that someone can help!

Kind regards,

Oussama